1. Field of the Invention
Embodiments disclosed herein relate to wellbore completion. More particularly, embodiments disclosed herein relate to providing a sealingly engaged connection between tubulars for completing a main or branch wellbore. Other embodiments disclosed herein pertain to activation of a swelling material to form a seal.
2. Description of the Related Art
Single or multiple branch wellbores are typically drilled and extended from a primary or main wellbore. The main wellbore can be vertical, deviated, or horizontal. Multibranch technology can be applied to both new and existing wells, and provides operators several benefits and economic advantages over drilling entirely new wells from the Earth's surface. For example, multibranch technology can allow isolated pockets of hydrocarbons, which might otherwise be left in the ground, to be tapped into. In addition, multibranch technology allows the improvement of reservoir production, increases the volume of recoverable reserves, and enhances the economics of marginal pay zones. By using multibranch technology, multiple reservoirs can be produced simultaneously, thus facilitating heavy oil production. Thin production intervals that might be uneconomical to produce alone become economical when produced together with multibranch technology. Consequently, it has become a common practice to drill deviated, and sometimes horizontal, branch boreholes from a main wellbore in order to increase production from a well.
In addition to production cost savings, development costs also decrease through the use of existing infrastructure, such as surface equipment and the wellbore. Multibranch technology expands platform capabilities where space is limited, and allows more wellbores to be added to produce a reservoir without requiring additional drilling and production space on the platform. In addition, by sidetracking depleted formations or completions, the life of existing wells can be extended. Finally, multibranch completions accommodate more wells with fewer footprints, making them ideal for environmentally sensitive or challenging areas.
The primary wellbore may be sidetracked to produce the branch borehole into another production zone. Further, a branch wellbore may be sidetracked into a common production zone. In sidetracking, a whipstock and mill assembly is used to create a window in the wall of the casing of a primary wellbore. The branch wellbore is then drilled through this window out into the formation where new or additional production can be obtained.
Once the branch wellbore has been drilled, various methods are employed for completing the well such that production via the branch wellbore can commence. For example, a tie-back assembly may be disposed adjacent the junction of the branch borehole and primary wellbore, as discussed in U.S. Pat. No. 5,680,901. The tie-back assembly and liner limit the exposure of the formation through the window cut in the casing. Similarly, U.S. Pat. No. 5,875,847 discloses a multibranch sealing device comprising a casing tool having a branch root premachined and plugged with cement. A profile receives a whipstock for the drilling of the branch borehole through the branch root and cement plug. A branch liner is then inserted and sealed within the branch root.
If the formation is a solid formation, the branch borehole need not include a casing or liner and may be produced open hole. If the branch borehole is unconsolidated or unstable and would tend to cave in, the branch borehole may be cased off or include a liner to support the formation. For example, it is common in the prior art to run and set a liner in the branch borehole with the liner extending from the flowbore of the casing and down into the branch borehole.
There are a variety of additional configurations that are possible when performing multibranch completions that “tie back” the branch for production. For example, U.S. Pat. No. 4,807,704 discloses a system for completing multiple branch wellbores using a dual packer and a deflective guide member. U.S. Pat. No. 2,797,893 discloses a method for completing branch wells using a flexible liner and deflecting tool. U.S. Pat. No. 3,330,349 discloses a mandrel for guiding and completing multiple branch wells. Another method of completing the branch wellbore involves sealing a dropped-off downole liner with a tubular that is advanced through the main wellbore into the opening of the dropped liner. This is usually achieved by a tube string having a bent joint and a guide means, such as a mule shoe device disclosed by U.S. Pat. No. 7,011,151.
When sections of production tubing are run into a wellbore, they are often landed in a liner hanger or a packer to interconnect the sections with previously run sections of production tubing. A seal assembly is secured to the lower end of the production tubing string being run that will create a bonded seal with a receptacle in the packer or liner hanger. Bonded seals for connecting tubulars and conduits together are well known in the art, and an example of a bonded seal is described in U.S. Pat. No. 6,142,538.
Previous landing arrangements have featured a muleshoe that is secured to the lower end of the seal assembly. In this type of arrangement, a beveled kickover lug is fashioned onto the outer surface of the end of the muleshoe to help guide the tip of the muleshoe into the opening of the receptacle.
However, a problem associated with landing the seal assembly into the receptacle is that the exact location of the entry or opening of the receptacle is often unknown. If the wellbore is deviated, the seal assembly tends to engage the edge of the receptacle instead of entering it. In order to correct the problem, it is often necessary to axially reciprocate and/or to rotate the production string in order to achieve proper seating. This operation is time consuming and costly and may be difficult to do if production tubing is being run from a floating rig that is prone to sea-induced motion or is equipped with control lines or cables for various completion accessories.
Similarly, this type of apparatus lacks flexibility in dealing with problems associated with branch wellbores because it requires a “close tolerance” fit for the bonded seal. For example, because the opening of the branch wellbore is usually at a significant depth within a formation, the exact location, orientation, and other general information about the opening are unknown. Thus, techniques have been sought to guide the seal assembly into a proper seating within the receptacle.
From the forgoing, it may be seen that it would be desirable to provide a means for forming a seal between two tubulars that overcomes the deficiencies of the prior art. Therefore, it may be seen that it would be beneficial to provide improved well completion systems and methods. Such systems and methods may include an improved seal between downhole tubulars.